1. Field of the Invention
The present invention relates to liquid containers for storing liquid, such as ink, and recording apparatuses using the liquid containers. More particularly, the present invention relates to a liquid container that can present various information using illumination of a light-emitting unit, such as a light-emitting diode (LED), and a recording apparatus using the liquid container.
2. Description of the Related Art
Recently, as digital cameras have come into widespread use, a recording method called non-PC recording in which a digital camera is directly connected to a printer that serves as a recording apparatus to perform a recording operation without using a personal computer (PC) has become popular. In addition, another type of non-PC recording in which a card-shaped information storing medium for a digital camera is directly attached to a printer for data transmission to perform a recording operation has also become popular. On the other hand, an amount of ink remaining in an ink tank of a printer is generally checked on a monitor using a PC. Accordingly, in non-PC recording, there is a demand to check the amount of ink remaining in the ink tank without using a PC. If a user recognizes that there is only a small amount of ink remaining in the ink tank, the user can replace the ink tank with a new ink tank before starting the recording operation, so that recording failure due to ink shortage can be prevented in the recording operation.
A typical structure for informing the user of the state of the ink tank includes a display element, such as an LED. Japanese Patent Laid-Open No. 4-275156 discloses a structure including two LEDs on an ink tank that is integrated with a recording head. The two LEDs are turned on in two steps in accordance with the amount of remaining ink. Similarly, Japanese Patent Laid-Open No. 2002-301829 discloses a structure including a lamp that is turned on in accordance with the amount of remaining ink. In the structure according to Japanese Patent Laid-Open No. 2002-301829, each of four ink tanks used in a recording apparatus has the lamp for informing the user of the amount of remaining ink.
On the other hand, to satisfy the requirements to record images with higher quality, ink of low-density colors, such as light magenta and light cyan, is used in addition to ink of four colors (black, yellow, magenta, and cyan). In addition, special color ink like red ink and blue ink is also used. In such a case, many ink tanks (for example, seven or eight ink tanks) are individually mounted in a recording apparatus. Accordingly, a mechanism for preventing each ink tank from being mounted at a wrong position is necessary. U.S. Pat. No. 6,302,535 discloses a structure in which engagement portions between mounting units and corresponding ink tanks have different shapes so that each ink tank is prevented from being attached at a wrong position when the ink tank is mounted on a carriage.
In general, because of manufacturing variations, LEDs may emit different amounts of light even when all the LEDs are connected to the same circuit and the same amount of current is applied. Therefore, the amount of light emitted from the LEDs provided on the ink tanks may differ for each LED. For example, when the LEDs on the ink tanks blink to inform the user that the amount of remaining ink is low, some of the LEDs may emit bright light while other LEDs emit dark light. In such a case, there is a risk that the user will regard the difference in brightness as the difference between the states of the ink tanks. For example, the user may think that a relatively large amount of ink is remaining in the ink tanks with bright LEDs and a small amount of ink is remaining in the ink tanks with dark LEDs. Thus, if there is a variation in brightness between the LEDs on the ink tanks, the user may mistakenly recognize that the difference in brightness has a certain meaning. This degrades the function of informing the user of the amount of remaining ink.
A similar problem also occurs when light-emitting elements other than LEDs are used. For example, when a lamp is provided on each of a plurality of ink tanks, the amount of light emitted from the lamps may differ for each lamp due to differences in performance thereof. Also in this case, the differences in visual brightness more easily occur as the number of ink tanks increases.